add CollectionProxy#first documentation

1 files changed, 27 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 03cbba8dea..401019e1f3 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -37,6 +37,33 @@ module ActiveRecord
       delegate :target, :load_target, :loaded?, :to => :@association
 
       ##
+      # :method: first
+      # Returns the first record, or the first +n+ records, from the collection.
+      # If the collection is empty, the first form returns nil, and the second
+      # form returns an empty array.
+      #
+      #   class Person < ActiveRecord::Base
+      #     has_many :pets
+      #   end
+      #
+      #   person.pets
+      #   # => [
+      #   #       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
+      #   #       #<Pet id: 2, name: "Spook", person_id: 1>,
+      #   #       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
+      #
+      #   person.pets.first # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>
+      #   person.pets.first(2)
+      #   # => [
+      #   #      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
+      #   #      #<Pet id: 2, name: "Spook", person_id: 1>
+      #   #    ]
+      #
+      #   another_person_without.pets          # => []
+      #   another_person_without.pets.first    # => nil
+      #   another_person_without.pets.first(3) # => []
+
+      ##
       # :method: concat
       # Add one or more records to the collection by setting their foreign keys
       # to the association's primary key. Since << flattens its argument list and